[SOLVED] What could happen if ESP32 uses GPIO 7/8 (shared with flash memory)

filo_gr
Posts: 110
Joined: Wed Jul 28, 2021 12:25 pm
Location: Italy

[SOLVED] What could happen if ESP32 uses GPIO 7/8 (shared with flash memory)

Postby filo_gr » Wed Mar 08, 2023 4:01 pm

Hello,

I'm using an ESP32-WROOM-32E with 16MB of Flash.

I'd like to understand how ESP32 effectively uses the pins from GPIO 6 to GPIO 11.

I know they are used for the flash memory chip inside, as said here viewtopic.php?t=1250.

I'm using a particular hardware, so not the ESP32-DevKit, where some hardware is connected to GPIO 7 and GPIO 8. It is working well and there aren't problems.
I flash the chip using the DIO mode.

My question is: why is it working? In my opinion it should give errors on the flash!
Last edited by filo_gr on Tue Mar 14, 2023 10:50 am, edited 2 times in total.
Filippo

ESP_Sprite
Posts: 9764
Joined: Thu Nov 26, 2015 4:08 am

Re: My ESP32 is using GPIO 7/8 (shared with flash memory)

Postby ESP_Sprite » Thu Mar 09, 2023 12:42 am

Well, first of all GPIO7 and 8 are not available on the castellated pads of that module; if you connect stuff to the pads where older modules had GPIO7/8, it won't affect the module. I'd still expect your program to crash when you run e.g. gpio_reset() on GPIO7/8 though.

filo_gr
Posts: 110
Joined: Wed Jul 28, 2021 12:25 pm
Location: Italy

Re: My ESP32 is using GPIO 7/8 (shared with flash memory)

Postby filo_gr » Tue Mar 14, 2023 7:49 am

ESP_Sprite wrote:
Thu Mar 09, 2023 12:42 am
Well, first of all GPIO7 and 8 are not available on the castellated pads of that module; if you connect stuff to the pads where older modules had GPIO7/8, it won't affect the module. I'd still expect your program to crash when you run e.g. gpio_reset() on GPIO7/8 though.
I was looking at the ESP32-WROOM-32 Datasheet v3.1, where from chapter 2 "Pin Definitions" I read that:
Pins SCK/CLK, SDO/SD0, SDI/SD1, SHD/SD2, SWP/SD3 and SCS/CMD, namely, GPIO6 to GPIO11 are connected to the integrated SPI flash integrated on the module and are not recommended for other uses.
However if I look at the new products e.g. ESP32-WROOM-32E Datasheet v1.6, I see that these pins aren't connected anymore (as you said)!

Thank you for this clarification!! :)
Filippo

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